Cutting elements are traditionally utilized for a variety of material removal processes, such as machining, cutting, and drilling. For example, tungsten carbide cutting elements have been used for machining metals and, to some degree, on drilling tools for drilling subterranean formations. Similarly, polycrystalline diamond compact (PDC) cutters have been used to machine metals (e.g., non-ferrous metals) and on subterranean drilling tools, such as drill bits, reamers, core bits, and other drilling tools. Other types of cutting elements, such as ceramic (e.g., cubic boron nitride, silicon carbide, and the like) cutting elements or cutting elements formed of other materials have also been utilized for cutting operations.
Drill bit bodies to which cutting elements are attached are often formed of steel or of molded tungsten carbide. Drill bit bodies formed of molded tungsten carbide (so-called matrix-type bit bodies) are typically fabricated by preparing a mold that embodies the inverse of the desired topographic features of the drill bit body to be formed. Tungsten carbide particles are then placed into the mold and a binder material, such as a metal including copper and tin, is melted or infiltrated into the tungsten carbide particles and solidified to form the drill bit body. Steel drill bit bodies, on the other hand, are typically fabricated by machining a piece of steel to form the desired external topographic features of the drill bit body.
In some situations, drill bits employing cutting elements may be used in subterranean mining to drill roof-support holes. For example, in underground mining operations, such as coal mining, tunnels must be formed underground. In order to make the tunnels safe for use, the roofs of the tunnels must be supported in order to reduce the chances of a roof cave-in and to shield mine workers from various debris falling from the roof. In order to support a roof in a mine tunnel, boreholes are typically drilled into the roof using a drilling apparatus. The drilling apparatus commonly includes a drill bit attached to a drilling rod. Roof bolts are then inserted into the boreholes to anchor a support panel to the roof.
Various types of cutting elements, such as PDC cutters, have been employed for drilling boreholes for roof bolts. Although other configurations are known in the art, PDC cutters typically comprise a substantially circular diamond “table” formed on and bonded (under high-pressure and high-temperature conditions) to a supporting substrate, such as a cemented tungsten carbide (WC) substrate.
As illustrated in FIG. 23, a conventional drill bit 120 for drilling roof-bolt boreholes may include two circular cutting elements 122 disposed radially outward relative to a central axis of drill bit 120. Unfortunately, the shape and orientation of cutting elements 122 on drill bit 120 may cause rifling of a borehole cut by drill bit 120. Further, cutting elements 122 may cause drill bit 120 to “walk” or wander across a surface to be drilled, rather than remaining centered at a desired point on the surface. Additionally, conventional drill bits having circular cutting elements may have a relatively small effective cutting surface relative to the diameter of the drill bit, reducing the overall effectiveness of the drill bit in cutting subterranean formations.